Sorry to hear that. You need to wait until you get your COPR at least before travel. Once you have COPR, you can go to CBSA to reteieve your passport and then you can ask someone to monitor your mailbox and send you your PR card to Jamaica by courrier. But if you leave before COPR, you will add a lot of delays to your case: need to apply for PR travel document at the Canadian embassy there + you may need Authorization to return to Canada because you had been issued deportation order.
One thing you can do is send an urgent email to Niagara to whomever was handling your file last time and explain the situation, attaching medical papers for your brother, asking nicely to speed up your case. Make sure to note your agent's ID, UCI and file number in subject line. Nothing is guaranteed with these guys, but you can try. However I strongly recommend to hang in here until COPR at least.